Associated production of a $W$-boson and a charm meson at NNLO in QCD

TL;DR

This work delivers differential NNLO QCD predictions for the associated production of a $W$ boson and a charm meson, $W^{\pm}D^{(*)\mp}$, at $\sqrt{s}=13$ TeV to illuminate the strange-quark content of the proton. It adopts collinear factorization with identified charm hadrons and fragmentation functions, employs OS-SS observables to suppress gluon-splitting backgrounds, and compares to ATLAS measurements, using PDF profiling to gauge sensitivity to $s$ and $\bar{s}$. NNLO corrections substantially reduce scale uncertainties to about $\pm5\%$ and improve both normalization and shape, though the $D^{*}$ channel exhibits a 5–10% overshoot likely tied to FF uncertainties; normalized distributions largely cancel perturbative and FF effects but remain PDF-sensitive. Profiling with MSHT20nnlo-_as118 and ATLASpdf21_T1 indicates tangible impacts on strange PDFs, supporting the inclusion of $W^{\pm}D^{(*)\mp}$ data in global fits and suggesting the possibility of jointly constraining PDFs and fragmentation functions with future FF inputs.

Abstract

The production of heavy-flavor hadrons in association with a vector boson in proton-proton collisions is a powerful probe for studying Quantum Chromodynamics and the content of protons. In this article, we provide, for the first time, differential predictions through NNLO for the production of $W^{\pm}D^{(*)\mp}$ final states. The results are compared to recent ATLAS measurements, and the sensitivity to the strange content of the proton is investigated by PDF profiling. The results are found to be promising for including $W^{\pm}D^{(*)\mp}$ measurements in proton-proton collisions in PDF fits.

Figures (11)

• Figure 1: Example Feynman diagrams for the leading partonic contributions for $W$ plus charm production.
• Figure 2: Lepton pseudo-rapidity distributions for $W^-D^+$ (top left), $W^+D^-$ (top right), $W^-D^{*+}$ (bottom left) and $W^+D^{*-}$ (bottom right). The top panel of each plot shows the LO (green), NLO (blue) and NNLO (red) theory predictions, with coloured bands indicating the scale uncertainties. The black data points show the ATLAS data ATLAS:2023ibp. The bottom panels show the NNLO predictions with three different sources of theory uncertainty: scale uncertainties (red), PDF errors (yellow), and FF errors (grey).
• Figure 3: As in Figure \ref{['fig:rapidity']}, but for the normalized distributions.
• Figure 4: As in Figure \ref{['fig:rapidity']}, but for the $D$-meson transverse momentum distributions.
• Figure 5: As in Figure \ref{['fig:transverse-momentum']}, but for the normalized distributions.